1. Field of the Invention
The present inventive concept relates to a laser scanning unit and a color image forming apparatus adopting the laser scanning unit.
2. Description of the Related Art
A laser scanning unit is an apparatus that forms electrostatic latent images by scanning laser beams onto a photosensitive drum in an image forming apparatus, such as a laser printer. A black-and-white laser printer only uses a laser scanning unit and one organic photoconductive cell (OPC) drum since only black color ink is transferred onto a print medium. In contrast, a color laser printer uses four laser scanning units and four OPC drums since inks of four colors, that is, black (K), magenta (M), yellow (Y), and cyan (C) colors, are respectively transferred onto a print medium. However, the laser scanning units incur the largest cost for manufacturing the color laser printer. Therefore, a way of reducing the manufacturing cost of color image forming apparatuses is to minimize the number of laser scanning units. Also, jitters generated by spindle motors that rotate polygonal rotating mirrors for each of the colors and periodic vibrations may be different from each other with respect to the four laser scanning units. Thus, when a line is printed on a medium, four colors are printed on different lines, thus degrading image quality. Therefore, in order to reduce manufacturing costs of the color image forming apparatus and to improve image quality, only one laser scanning unit is used to form color images.
However, scanning lines imaged on each of the photosensitive drums may be curved. When forming the color images, it is important to correct curvature of a scanning line of each single color; however, relative error of the scanning line curvature generated when each of the scanning lines are combined together may cause a severe problem when color images are formed. Therefore, a method and a configuration to correct the scanning line curvature with respect to each of the colors in order to have the same curvature amount in the same direction as each other have been variously suggested.